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Commit cd95ea81 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

x86/fpu, lguest: Remove CR0.TS support 



Now that Linux never sets CR0.TS, lguest doesn't need to support it.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm list <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/8a7bf2c11231c082258fd67705d0f275639b8475.1477951965.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 04ac88ab

arch/x86/include/asm/lguest_hcall.h

+0 −1
Original line number Diff line number Diff line
@@ -9,7 +9,6 @@ 
#define LHCALL_FLUSH_TLB	5

#define LHCALL_LOAD_IDT_ENTRY	6

#define LHCALL_SET_STACK	7

#define LHCALL_TS		8

#define LHCALL_SET_CLOCKEVENT	9

#define LHCALL_HALT		10

#define LHCALL_SET_PMD		13

arch/x86/lguest/boot.c

+7 −10
Original line number Diff line number Diff line
@@ -497,27 +497,24 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx, 
 * a whole series of functions like read_cr0() and write_cr0().

 *

 * We start with cr0.  cr0 allows you to turn on and off all kinds of basic

 * features, but Linux only really cares about one: the horrifically-named Task

 * Switched (TS) bit at bit 3 (ie. 8)

 * features, but the only cr0 bit that Linux ever used at runtime was the

 * horrifically-named Task Switched (TS) bit at bit 3 (ie. 8)

 *

 * What does the TS bit do?  Well, it causes the CPU to trap (interrupt 7) if

 * the floating point unit is used.  Which allows us to restore FPU state

 * lazily after a task switch, and Linux uses that gratefully, but wouldn't a

 * name like "FPUTRAP bit" be a little less cryptic?

 * lazily after a task switch if we wanted to, but wouldn't a name like

 * "FPUTRAP bit" be a little less cryptic?

 *

 * We store cr0 locally because the Host never changes it.  The Guest sometimes

 * wants to read it and we'd prefer not to bother the Host unnecessarily.

 * Fortunately, Linux keeps it simple and doesn't use TS, so we can ignore

 * cr0.

 */

static unsigned long current_cr0;

static void lguest_write_cr0(unsigned long val)

{

	lazy_hcall1(LHCALL_TS, val & X86_CR0_TS);

	current_cr0 = val;

}



static unsigned long lguest_read_cr0(void)

{

	return current_cr0;

	return 0;

}



/*

drivers/lguest/hypercalls.c

+0 −4
Original line number Diff line number Diff line
@@ -109,10 +109,6 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) 
	case LHCALL_SET_CLOCKEVENT:

		guest_set_clockevent(cpu, args->arg1);

		break;

	case LHCALL_TS:

		/* This sets the TS flag, as we saw used in run_guest(). */

		cpu->ts = args->arg1;

		break;

	case LHCALL_HALT:

		/* Similarly, this sets the halted flag for run_guest(). */

		cpu->halted = 1;

drivers/lguest/lg.h

+0 −1
Original line number Diff line number Diff line
@@ -43,7 +43,6 @@ struct lg_cpu { 
	struct mm_struct *mm; 	/* == tsk->mm, but that becomes NULL on exit */



	u32 cr2;

	int ts;

	u32 esp1;

	u16 ss1;

drivers/lguest/x86/core.c

+1 −18
Original line number Diff line number Diff line
@@ -246,14 +246,6 @@ unsigned long *lguest_arch_regptr(struct lg_cpu *cpu, size_t reg_off, bool any) 
 */

void lguest_arch_run_guest(struct lg_cpu *cpu)

{

	/*

	 * Remember the awfully-named TS bit?  If the Guest has asked to set it

	 * we set it now, so we can trap and pass that trap to the Guest if it

	 * uses the FPU.

	 */

	if (cpu->ts && fpregs_active())

		stts();



	/*

	 * SYSENTER is an optimized way of doing system calls.  We can't allow

	 * it because it always jumps to privilege level 0.  A normal Guest
@@ -282,10 +274,6 @@ void lguest_arch_run_guest(struct lg_cpu *cpu) 
	 if (boot_cpu_has(X86_FEATURE_SEP))

		wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);



	/* Clear the host TS bit if it was set above. */

	if (cpu->ts && fpregs_active())

		clts();



	/*

	 * If the Guest page faulted, then the cr2 register will tell us the

	 * bad virtual address.  We have to grab this now, because once we
@@ -421,12 +409,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu) 
			kill_guest(cpu, "Writing cr2");

		break;

	case 7: /* We've intercepted a Device Not Available fault. */

		/*

		 * If the Guest doesn't want to know, we already restored the

		 * Floating Point Unit, so we just continue without telling it.

		 */

		if (!cpu->ts)

			return;

		/* No special handling is needed here. */

		break;

	case 32 ... 255:

		/* This might be a syscall. */